1,195 research outputs found
Performance of a 20-cm-diameter Electron Bombardment Hollow Cathode Ion Thruster
Electron bombardment hollow cathode ion thruster performanc
Plasma device feed system Patent
Nonconductive tube as feed system for plasma thrusto
A Preliminary Investigation of the Performance of a Short-length Turbojet Combustor Using Vaporized Hydrocarbon Fuels
Two short turbojet combustors designed for use with vaporized hydrocarbon fuels were tested in a one-quarter annular duct. The experimental combustors consisted of many small "swirl-can" combustor elements manifolded together. This design approach allowed the secondary mixing zone to be considerably reduced over that of conventional combustors. The over-all combustion lengths, for the two configurations were 13.5 and 11.0 inches, approximately one-half the length of the shortest conventional combustors. These short combustors did not provide combustion efficiencies as high as those for conventional combustors at low pressures. However, over the range of combustor-inlet total-pressures expected in aircraft capable of flight at Mach numbers of 2.5 and above, these short combustors gave very high efficiencies. A combustion efficiency of 97 percent was obtained at a combustor-inlet total-pressure of 25.0 inches of mercury absolute, reference velocity of 120 feet per second, and inlet-air total temperature of 1160 deg R. By proportioning the fuel flow between the manifold rows of can combustor elements, control of the combustor-outlet radial total-temperature profile was demonstrated. Combustor totalpressure loss varied from 0.75 percent of the inlet total pressure at isothermal conditions and a reference velocity of 75 feet per second to 5.5 percent at a total-temperature ratio of 1.8 and a reference velocity of 180 feet per second
Preliminary investigations of ion thruster cathodes
Mercury vapor fed hollow cathodes for electron bombardment ion thruster
Sandblasting nozzle
A nozzle for use with abrasive and/or corrosive materials is formed of sintered ceramic compositions having high temperature oxidation resistance, high hardness and high abrasion and corrosion resistance. The ceramic may be a binary solid solution of a ceramic oxide and silicon nitride, and preferably a ternary solid solution of a ceramic oxide, silicon nitride and aluminum nitride. The ceramic oxide is selected from a group consisting of Al2O3, Y2O3 and Cr2O3, or mixtures of those compounds. Titanium carbide particles are dispersed in the ceramic mixture before sintering. The nozzles are encased for protection from external forces while in use by a metal or plastic casing
Simulation of an ion thruster control system
The results of an initial effort to model the control loops of a 30-cm diameter electron bombardment thruster and a transistorized power processor predicting its operation were described. Data from which the model is made is presented as well as comparisons between the computer outputs and test data from the JPL Solar Electric Propulsion systems laboratory
A technique for obtaining plasma-sheath configurations and ion optics for an electron- bombardment ion thrustor
Plasma boundaries and ion trajectories for accelerator system of electron bombardment ion thrusto
Solar electric propulsion system tests
Design and performance of solar-powered electric propulsion system for interplanetary space exploratio
Fast Large-Scale Reionization Simulations
We present an efficient method to generate large simulations of the Epoch of
Reionization (EoR) without the need for a full 3-dimensional radiative transfer
code. Large dark-matter-only simulations are post-processed to produce maps of
the redshifted 21cm emission from neutral hydrogen. Dark matter haloes are
embedded with sources of radiation whose properties are either based on
semi-analytical prescriptions or derived from hydrodynamical simulations. These
sources could either be stars or power-law sources with varying spectral
indices. Assuming spherical symmetry, ionized bubbles are created around these
sources, whose radial ionized fraction and temperature profiles are derived
from a catalogue of 1-D radiative transfer experiments. In case of overlap of
these spheres, photons are conserved by redistributing them around the
connected ionized regions corresponding to the spheres. The efficiency with
which these maps are created allows us to span the large parameter space
typically encountered in reionization simulations. We compare our results with
other, more accurate, 3-D radiative transfer simulations and find excellent
agreement for the redshifts and the spatial scales of interest to upcoming 21cm
experiments. We generate a contiguous observational cube spanning redshift 6 to
12 and use these simulations to study the differences in the reionization
histories between stars and quasars. Finally, the signal is convolved with the
LOFAR beam response and its effects are analyzed and quantified. Statistics
performed on this mock data set shed light on possible observational strategies
for LOFAR.Comment: 18 pages, 21 figures, submitted to MNRAS For high-resolution images
follow "http://www.astro.rug.nl/~thomas/eormap.pdf
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